Switch actuating device



March 30, 1965 E. J. SCHAEFER SWITCH ACTUATING DEVICE Filed Oct. 18,1962 INVENTOR. Edward, J5me:

BY y United States Patent Ofiice 3,l75,4l8 Patented Mar. 30, 19553,175,418 SWITCH ACTUATING DEVHZE Edward J. Schaefer, Blutfton, Ind,assignor to Franklin Electric Co., Inc, Bluifton, End, a corporation ofIndiana Filed Oct. 18, 1962, Ser. No. 231,469 15 Claims. (Cl. 74-4248)This invention relates to a novel actuating device for a switch such asa limit switch.

Frequently a drive unit for a device is provided with a control toprevent the device from being driven beyond predetermined limits. Onecommon type of control includes a switch positioned to be actuated by anactuating means when the device is driven in one direction to a limit,the switch being connected to prevent the device from being drivenfarther in that direction when the limit is reached. In somecircumstances, it has been found that, after the limit switch has beenactuated, the actuating means has a tendency to drift back a smallamount in the reverse direction, and if this drift is sufficient theactuating means may permit the limit switch to deactuate. Deactuation ofthe limit switch is generally undesirable because it may cause power toagain be connected to the device, which in some circumstances will leadto hunting or to some other undesired movement of the device. Thisproblem is particularly acute when a switch having slow break contactsis used.

Accordingly, a primary object of this invention is to provide anactuating means for a limit switch, which will hold the limit switchopen even though the actuating means drifts a small amount back from thelimit.

Another object is to provide a switch actuating means which permits theuse of a limit switch of a simple and inexpensive type having slow breakcontacts.

Other objects and advantages of the invention will become apparent fromthe following description taken in conjunction with the accompanyingfigures of the drawing, in which:

. FIG. 1 is an end elevational view of apparatus including an actuatingmeans embodying the invention;

FIG. 2 is a view taken along the line 2-2 of FIG. 1;

FIG. 3 is a side elevational view of part of the actuating device;

FIG. 4 is a view taken on the line 4-4 of FIG. 1; and

FIG. 5 is a view similar to FIG. 4 but showing a different position ofthe parts.

In general, a switch actuating means embodying the invention is adaptedto be used in a system including a drive unit for a device and a limitswitch. The actuating means includes a nut element adjacent an actuatorelement for the switch, and the system is designed such that, as thedevice is driven, the nut element and the switch actuator element aremoved relative to each other along a path toward each other until thenut element engages and displaces the actuator element, and actuates thelimit switch. After the nut and the actuator are brought intoengagement, they may be moved a first predetermined distance along thepath away from each other, due to drift. In that event, the nut elementis rotatively moved laterally of said path a second predetermineddistance. One of the nut and actuator elements includes means forincreasing the displacement of said switch actuator element when saidlateral movement occurs. In the present instance, this means is formedon the nut element, and comprises a cam surface which is the portion ofthe nut element engaging the actuator element. This cam surface slopestoward the switch actuator element from the point of initial engagementwith said actuator element. The lateral movement of the cam surface andthe switch actuator element relative to each other causes the switchactuator element to slide along the sloped cam surface said secondpredetermined distance. The slope of the cam surface is such that itsrise during movement through the second predetermined distance increasesthe displacement of said actuator element. The increase in displacementis preferably substantially equal to said first predetermined distance,which is the distance the switch actuator element and the nut elementdrift away from each other. Accordingly, the switch is maintainedactuated even though relative movement of the switch actuator elementand the nut element is in a direction away from each other.

In greater detail, in FIGS. 1 and 2 there is shown a shaft 1i rotatablymounted on a frame 9, the shaft It) being adapted to be connected in asystem including a drive unit and a device driven by the drive unit (notshown in the drawings). Systems including drive units for the functionssuitable for use with actuators embodying the invention are disclosed inmy pending applications Serial No. 61,758, now Pat. No. 3,134,469, filedOctober 10, 1960, entitled Drive Unit Control System, and Serial No.40,959, now Pat. No. 3,129,607, filed July 5, 1960, entitled Drive Unitand Control. It should be clearly understood, however, that a switchactuating device embodying the present invention is not limited to usein the systems described in these two pending applications.

The shaft ll is connected to the driven device such that it rotates asthe device is driven, the shaft rotating clockwise, in this instance,when the device is driven in one direction and the shaft rotatingcounterclockwise when the device is driven in the other direction.Secured to the outer surface of the shaft it! is an externally threadedsleeve 11 which is coaxial with the shaft it In the event the use of thesleeve 11 is undesirable, it may be omitted and the exterior of theshaft 10 may be threaded.

Two internally threaded identical limit switch nuts 12 and 13 arethreaded onto the sleeve 11. Each nut comprises a central hub ormounting portion 14 having a bore 16 formed therethrough. This bore isprovided with threads of the same type and pitch as those of the sleeve11. Three radially and axially extending grooves 17 (FIG. 1) may beformed in the bore 16, these grooves being provided to allow some selfcleaning and to prevent the nut 12 from tightening on the threads of thesleeve 11.

The nut 12 also includes four equally spaced, radially extending flanges18, which form four notches 19 (FIG. 1) therebetween. With specificreference to FIGS. 2 and 3, one surface 21 of each flange 18 is normalto the axis of the nut and the opposite surface 22 forms an angle withrespect to a plane normal to the nut axis. The angled surface 22 isemployed as a cam surface for engaging a switch actuator hereinafterdescribed. Due to the angle of the surface 22 relative to the oppositesurface 2 1, each flangehas a thin edge 23 and a thick edge 24 (FIGS. 4and 5).

With reference to FIG. 2, the two nuts 12 and 13 are threaded onto thesleeve ll in axially spaced relation. A guide '26 is secured to theframe 9 as by screws 27, and includes an axially extending guide arm 28.This arm 23 is positioned within one of the four notches 19 of each nut12 and 13 and the width of the arm 28 is less than the width of thenotches 19, preferably approximately one-half of such width. It isapparent that, as the shaft 10 and the sleeve 11 rotate, for example inthe clockwise direction, the friction between the sleeve 11 and the nuts12 and 13 causes the nuts to be urged in the clockwise direction also.As soon as an edge of one of the flanges 18 contacts the guide arm 23,the nuts are prevented from further rotation, and the nuts then moveaxially of the shaft It in sliding engagement with the arm 28 as theshaft continues to rotate.

Two limit switches 31 and 32 are also provided, the two switches beingmounted in axially spaced relation on the frame 9. The switch mountingapparatus, in this instance, is shown as including two blocks 33 and 34,two bolts 35, and spacers 36 and 37 which maintain the blocks 33 and 34away from each other and away from the frame 9. The blocks and thespacers are preferably made of insulating material. Each switch 31 and32 includes a spring arm 38 and a fixed arm 39 fastened to the blocks 33and 34, and each arm 38 and 39 includes a contact 41. The lower end ofeach switch arm may be provided with a tab for electrically connectingthe switch arms into the control system. The outer end of each springarm 38 extends beyond the fixed arm 39 and forms a switch actuator 41and the two spring arms 38 are mounted on the outward sides of the fixedarms 39. The nuts 12 and 13 are positioned on the sleeve 11 between theswitch actuator lh and with the cam surfaces 22 of the flanges 18 facingoutwardly.

When the shaft 19 rotates clockwise, the two nuts 12 and 13 move axiallytoward the left as shown in FIG. 2, and the limit switch 31 ispositioned such that the cam surface 22 of one of the flanges 13 of thenut =12 engages the switch actuator 40 of the switch 31. When the shaft10 rotates counterclockwise, the two nuts 12 and 13 move axially towardthe right, and the limit switch 32 is positioned such that the camsurface 22 of one of the flanges 18 of the nut 13 engages the switchactuator 41 of the switch 32. When a flange 18 engages one of theactuators 40, the arm 38 is forced outwardly away from the fixed arm 39,thereby breaking connection between the contacts 41 of that switch.While the switches are shown and described as normally closed types, itis apparent that normally open switches could also be used, by mountingthe switches with the spring arms on the inward sides of the fixed arms.As previously mentioned, the nuts 12 and '13 are mounted with the camsurfaces 22 of the flanges 17 facing outwardly, so that it is thesesurfaces which engage the switch actuators 46. Each switch actuator 41)is preferably formed with an inwardly facing tapered ridge 42 (FIGS. 2,4 and 5) which engages-the cam surface 22, and the guide arm 28 holdsthe nuts 12 and 13 such that the ridges 42 initially engage the camsurface 22 of a nut adjacent the thin edge 23 of a flange 18.

In operation, assume a system wherein the shaft is coupled to a driveunit and to a device being driven, and the limit switches 31 and 32 areconnected in a control circuit for the system. The switches 31 and 32are preferably connected to either deenergize a drive motor or a clutch,or both, upon opening. When the shaft 11 is rotated in the clockwisedirection, a side of one of the flanges 18 of each nut 12 and 13 engagesthe stationary guide arm 28 which prevents the nuts from rotating, andthe nuts 12 and 13 move axially toward the left as seen in FIG. 2 untila flange 18 of the nut 12 engages the switch actuator 40 of the switch31 and opens this switch. As shown in FIG. 4 and previously mentioned,the flange 18 initially engages the ridge 42 adjacent the thin edge 23of the flange. The switch 31 is preferably connected in the controlcircuit such as to disconnect power from the device and cause the shaft111 to stop rotating when it opens. If, for any reason, the shaft 10subsequently drifts back in the counterclockwise direction after theswitch 3 1 has been opened, the nuts 12 and 13 will also rotate in thisdirection with shaft 10 until the side of the flange adjacent thepreviously engaged flange in the clockwise direction engages the guidearm 28, which prevents counterclockwise rotation of the nuts 12 and 13beyond an angle of approximately 25. This movement back of the nut 12causes the ridge 42 of the switch 31 to slide up the cam surface 22 to aposition adjacent the thick edge 24 of the flange 18 as shown in FIG. 5.Due to slope of the cam surface 22, the contacts 41 of the switch arms33 and 39 are moved farther apart than before. Therefore, even thoughthe shaft ltl drifts in the counterclockwise direction and the nut 12moves toward the right a small amount, the switch 31 will continue to beheld open.

The amount of counterclockwise rotation of the shaft 10 permitted beforethe switch 31 closes is determined by the pitch of the threads of thesleeve 11, the slope of the cam surface 22 of the flanges 18, and thedifference between the widths of the guide arm 25 and the notches 19between the flanges 18.

In a specific embodiment of the invention, the pitch of the threads ofthe sleeve 11 and the nuts 12 and 13 is forty four threads to the inch.The width of the slots 19 is inch and the width of the guide arm 28 isinch, and the surface 22 makes an angle of 7i20 with a plane normal tothe axis of the nut. This construction permits approximately onecomplete revolution back of the shaft 10 without closing of the switch31. Of course, he width of the flanges 18 must be greater than thedifference in width between the notches 19 and the guide arm 28 so thatthe ridge 42 will not slide off the flange 18 when the nut rotates back.

The rise of the cam surface 22 is preferably designed to beapproximately equal to the expected amount of axial drift back of thenut. With reference to the construction describe-d when the shaft 19moves counterclockwise, the flange 18 moves laterally of the switch arm38 a predetermined amount which is equal to the difference in Widthbetween the guide arm 2% and the slot 19. The rise of the slope 22 overthis distance is equal to the amount by which the contacts 41 areinitially moved farther apart. If the shaft 10 drifts back approximatelyone revolution, the nut 12 will move axially toward the rightapproximately the pitch of the threads of the sleeve 11 and the nut 12.It is apparent that, if the rise of the cam surface 22 over the abovelateral distance is made approximately equal to the axial movement backof the nut 12, or the pitch of the threads, the switch contacts 41 Willbe in the same position as they were before the drift back of the shaft10 occurred.

One type of system in which an actuating device embodying the presentinvention is useful is described in the previously mentioned applicationSerial No. 61,758. That application covers a control system for a driveunit of the type described in the other previously mentioned applicationSerial No. 40,959. The system of the former application comprises onereversible electric motor that is selectively connectible by a pluralityof clutches to a plurality of shafts for driving diiferent functions.For example, the shafts may be for driving different mechanisms of ahospital bed, such as one for raising and lowering the head, one forraising and lowering the foot, and one for raising and lowering the bedas a whole. Limit switch nuts embodying the invention may be used inplace of the huts 121 and 122 of application Serial No. 40,959.

A drift back of the shaft carrying the limit switch nuts, as describedin the present application, may occur when the shaft is connected todrive the bed height function, and the control system shown in FIG. 1 ofapplication Serial No. 61,758 is used to control the drive unit, thecontroller or handle 153 of FIG. 2 being used however instead of thehandle 91. With reference to this last mentioned application, if toggleswitch 149 is turned to the full line position shown in FIG. 1, relaycoil 129 will be energized and relay contact 69 will close. Solenoidcoil 18 is then energized which engages the clutch for this function,and power is also connected to the motor windings 22 and 23. The bed isthen driven upwardly until the limit switch 87 opens and deenergizes theclutch coil 18 and the motor windings 22 and 23.

The type of clutch described in application Serial No. 40,959 is onewhich may engage or disengage only in increments of one revolution ofthe drive shaft. Unless a cam shown in that application is at a certainposition, the clutch cannot disengage even though the solenoid coil (79in Serial No. 40,959, 18 in Serial No. 61,758) is deenergized by theopening of the limit switch (107 or 108 in Serial No. 40,959, 83 or 87in Serial No. 61,758).

Assuming that the condition exists where the limit switch 87 (of SerialNo. 61,758) is open but the bed height function clutch associated withcoil 18 is still engaged, it may subsequently be desired to lower thefoot of the bed. This is accomplishd by pressing switch 97a which closescircuits to energize the drive motor in the direction opposite itsdirection when the bed was raised. Since the clutch for the bed heightfunction is still engaged, the drive shaft for this function will rotatea partial revolution back until the drive shaft is at the point wherethis clutch will disengage. As described in the present application, thepartial revolution back of the shaft moves the limit switch nut awayfrom the limit switch. If an ordinary type nut is used, the limit switchmay close again. If it doe close, as soon as the switch 97a is releasedpower is applied to terminal 163, and the coils 129 and 18 are againenergized, unintentionally, because the toggle switch 149 is stillturned to the right. The bed will then be raised again until the limitswitch 37 is opened. This difiiculty is eliminated when using a limitswitch nut embodying the present invention because the drive shaft forthe bed height function may move a partial revolution back without thelimit switch closing.

It should be understood that an actuating device embodying the inventionis not limited to use with the fore going systems. It may be usedwhenever a surface is used to engage and actuate a limit switch.

I claim:

1. Switch actuating means for use in a control system for a drive unitfor a driven device, comprising an externally threaded member adapted tobe connected to the drive unit and be rotated as the drive unit drivessaid device, a nut threaded on said member, means engaging said nut andpermitting axial movement of said nut due to the rotation of saidmember, said means preventing rotation of said nut as said member isrotated in one direction but permitting rotation of said nut through apredetermined are when said member is rotated in the other direction,and an actuator for a switch positioned to be engaged by said nut whensaid member is rotated in said one direction a predetermined amount,said rotation causing said nut to move axially toward and engage anddisplace said switch actuator, said nut having means for increasing thedisplacement of said switch actuator on rotation of said nut in saidother direction through said predetermined are.

2. Switch actuating means for use in a control system for a drive unitfor a driven device, comprising an externally threaded member adapted tobe connected to the drive unit and be rotated as the drive unit drivessaid device, a nut element threaded on said member, means engaging saidnut element and permitting axial movement of said nut element due torotation of said member, said means preventing rotation of said nutelement as said member is rotated in one direction but permittingrotation of said nut element through a predetermined are when saidmember is rotated in the other direction, a switch actuating elementpositioned to be engaged by said nut element when said member is rotatedin said one direction a predetermined amount, said rotation causing saidnut element to move axially toward and engage and dis-place said switchactuating element, one of said elements having means for increasing thedisplacement of said switch actuating element when said member and saidnut element are rotated in said other direction through saidpredetermined are.

3. Switch actuating means as in claim 2, wherein said means forincreasing said displacement of said switch actuating element comprisesa cam surface.

4. Switch actuating means for use in a control system for a drive unit,for a driven device comprising an externally threaded member adapted tobe connected to the drive unit and be rotated as the drive unit drivessaid device, a nut threaded on said member, said nut including a camsurface on one side, means engaging said nut and permitting axialmovement of said nut, due to rotation of said member, said meanspreventing rotation of said nut as said member is rotated in onedirection but permitting rotation of said nut through a predeterminedare when said member is rotated in the other direction, and an actuatorfor a switch positioned to be engaged by said cam surface when saidmember is rotated in said one direction a predetermined amount, saidrotation causing said nut to move axially toward and engage and displacesaid switch actuator, said cam surface sloping toward said switchactuator from its point of initial engagement with said switch actuator,whereby rotation of said member and said nut in said other directionthrough said predetermined arc causes said switch actuator to slidealong said sloped cam surface and increase the displacement of saidswitch actuator.

5. A switch actuating device as in claim 4, wherein said nut furtherincludes at least one radially outward extending flange, and said camsurface is formed on one side of said flange.

6. A switch actuating device as in claim 4, wherein said nut furtherincludes at least one slot formed at its outer periphery, said meansengaging said nut comprises a guide, and said guide includes an armpositioned in said slot.

7. A switch actuating device as in claim 4, wherein said nut furtherincludes a plurality of radially and axially extending grooves formed inits inner periphery, said grooves rendering said nut self cleaning andpreventing tightening of said nut on said threaded member.

8. A switch actuating device as in claim 4, wherein said nut movesaxially away from said switch actuator a predetermined distance whensaid member is rotated in said other direction and said nut rotatesthrough said predetermined arc, and the rise of said cam surface duringmovement through said predetermined arc is substantially equal to saidpredetermined distance.

9. A switch actuating device as in claim 4, wherein said nut furtherincludes at least one slot formed in its outer periphery, and said guideincludes an arm positioned in said slot, said predetermined are beingequal to the difference in width between said arm and said slot.

10. A switch actuating device as in claim 4 and further including aswitch having a fixed arm and a spring arm, and said switch actuatorcomprises the outer end of said spring arm.

11. A switch actuating device as in claim 10, wherein said switchactuator includes a raised portion positioned to engage said cam surfaceof said nut.

12. A limit switch actuating means for use in a system including a driveunit, a device driven by the drive unit, and a limit switch, saidactuating means comprising a mounting portion, and at least one flangeportion attached to and extending outwardly from said mounting portion,said portions being adapted to be moved in a forward direction towardthe limit switch as the device is driven until said flange portionengages and actuates the limit switch, and said portions being adapted.to be subsequently moved in the rearward direction away from the limitswitch a first predetermined distance and said flange portion beingadapted to be moved laterally of the limit switch a second predetermineddistance, said flange portion being formed such that it slopes in saidforward direction from the point of initial engagement with the limitswitch and the limit switch is adapted to slide on said slope as saidflange portion is moved laterally said second predetermined distance,the rise of said slope through said second predetermined distance beingsubstantially equal to said first predetermined distance, where by saidlimit switch remains actuated even though said actuator moves in saidrearward direction away from the limit switch substantially said firstpredetermined distance.

13. A nut for use in a system including a drive unit having a threadeddrive shaft, a device driven by the drive unit, a guide for limiting therotative movement of the nut but permitting aXial movement of the nut,and a limit switch, said nut comprising an internally threaded hubadapted to be mounted on said shaft and having at least one radiallyextending flange, said nut being adapted to be moved in a forwarddirection toward the limit switch as the device is driven with saidflange adapted to engage and displace the limit switch, and said nutbeing adapted to be subsequently moved in the rearward direction awayfrom the limit switch a first predetermined distance and said flangebeing adapted to rotate with said shaft and thereby be moved laterallyof the limit switch a second predetermined distance, said flange beingformed such that it slopes in said forward direction from the point ofinitial engagement with the limit switch and the limit switch is adaptedto slide on said slope as said flange is moved laterally said secondpredetermined distance, the rise of said slope through said secondpredetermined distance being at least substantially equal to said firstpredetermined distance, whereby said limit switch remains displaced eventhough said nut moves in said rearward direction away from the limitswitch substantially said first predetermined distance, said nut havingmeans adapted to be engaged by said guide.

14. A nut as in claim 13, wherein said hub includes a plurality ofradially and axially extending internal grooves, said grooves renderingsaid nut self cleaning.

15. Switch actuating means for use in a control system for a drive unitfor a driven device, comprising a member adapted to be connected to thedrive unit and be moved as the drive unit drives said device, anactuator element connected to said member, a switch actuating element,said member being adapted to move said actuator element in a forwarddirection toward said switch actuating element as the drive unit drivessaid device until said actuator element engages and displaces saidswitch actuating element, said actuator element being adapted to besubsequently moved by said member laterally of said switch actuatingelement a first predetermined distance and to be moved in a rearwarddirection away from said switch actuating element a second predetermineddistance, means engaging said actuator element and eflective to causesaid actuator element to move in said forward and rearward directionsand to cause said lateral movement on changing its movement from saidforward to said reverse directions, one of said elements having meansfor increasing the displacement of said switch actuating element whensaid actuator element is moved laterally through said firstpredetermined distance, said increase in displacement being at leastsubstantially equal to said second predetermined distance, whereby saidswitch actuating element remains displaced even though said actuatingelement moves in said rearward direction said second predetermineddistance.

References Cited by the Examiner UNITED STATES PATENTS 1,601,346 9/26Callahan 20047 2,253,557 8/41 Collins 200-47 2,276,740 3/42 Saito200-458 2,773,966 12/56 Mastropole 74-424.8 XR 2,951,920 9/60 Miller200-47 FOREIGN PATENTS 6,425 1888 Great Britain.

DON A. WAITE, Primary Examiner.

1. SWITCH ACTUATING MEANS FOR USE IN A CONTROL SYSTEM FOR A DRIVE UNITFOR A DRIVEN DEVICE, COMPRISING AN EXTERNALLY THREADED MEMBE ADAPTED TOBE CONNECTED TO THE DRIVE UNIT AND BE ROTATED AS THE DRIVE UNIT DRIVESSAID DEVICE, A NUT THREADED ON SAID MEMBER, MEANS ENGAGING SAID NUT ANDPERMITTING AXIAL MOVEMENT OF SAID NUT DUE TO THE ROTATION OF SAIDMEMBER, SAID MEANS PREVENTING ROTATION OF SAID NUT AS SAID MEMBER ISROTATED IN ONE DIRECTION BUT PERMITTING ROTATION OF SAID NUT THROUGH APREDETERMINED ARC WHEN SAID MEMBER IS ROTATED IN THE OTHER DIRECTIONKAND AN ACTUATOR FOR A SWITCH POSITIONED TO BE ENGAGED BY SAID NUT WHENSAID MEMBER IS ROTATED IN SAID ONE DIRECTION A PREDETERMINED AMOUNT,SAID ROTATION CAUSING SAID NUT TO MOVE AXIALLY TOWARD AND ENGAGE ANDDISPLACE SAID SWITCH ACTUATOR, SAID NUT HAVING MEANS FOR INCREASING THEDISPLACEMENT OF SAID SWITCH ACTUATOR ON ROTATION OF SAID NUT IN SAIDOTHER DIRECTION THROUGH SAID PREDETERMINED ARC.